How to calculate a pie chart angle
A pie chart divides a full circle among categories in proportion to their values. A full circle is 360 degrees, so each category's slice angle is simply its share of the total multiplied by 360:
Slice angle (degrees) = (category value / total of all values) × 360
Every slice is a fraction of the whole. If a category represents 25 out of a grand total of 200, its share is 25 / 200 = 0.125, so its angle is 0.125 × 360 = 45 degrees. Because the fractions of all categories add up to 1, the angles always add up to 360 degrees.
Worked example
Suppose a monthly budget of $2,000 splits into Rent $900, Food $500, Transport $300, and Savings $300. The angle for each slice is its amount divided by 2,000, times 360:
- Rent: (900 / 2000) × 360 = 162° (45%)
- Food: (500 / 2000) × 360 = 90° (25%)
- Transport: (300 / 2000) × 360 = 54° (15%)
- Savings: (300 / 2000) × 360 = 54° (15%)
The four angles sum to 162 + 90 + 54 + 54 = 360 degrees, which confirms the arithmetic.
Why you need it
When you draw a pie chart by hand or with a protractor, you have to know how many degrees each wedge occupies. Spreadsheet tools do this automatically, but the angle is still the underlying quantity, and knowing it lets you check a chart, mark a wedge precisely, or convert a percentage back into the geometry of the circle.
Handy reference points
A few percentages map to angles worth memorizing: 100% is 360°, 50% is 180° (a half circle), 25% is 90° (a right angle), 10% is 36°, and 1% is 3.6°. To go from a percentage straight to an angle, multiply the percentage by 3.6.
Frequently Asked Questions
How do you calculate the angle of a pie chart slice?
Do all the slice angles add up to 360 degrees?
How do I convert a percentage into a pie chart angle?
What total should I use?
Common Tip Percentages
| Service | Typical Tip Range | Notes |
|---|---|---|
| Restaurant (sit-down) | 15–20% | 20%+ for exceptional service |
| Food delivery | 10–20% | Consider extra for long distances |
| Taxi / rideshare | 10–20% | More for assistance with luggage |
| Hotel housekeeping | $2–5/night | Leave daily, not just at checkout |
| Barber / hair salon | 15–20% | On pre-discount total |
| Pizza delivery | 10–15% or $3–5 minimum | Higher in bad weather |
General Household Budget Ratios (50/30/20 Rule)
| Category | % of Net Income | Examples |
|---|---|---|
| Needs | 50% | Rent, groceries, utilities, insurance |
| Wants | 30% | Dining out, entertainment, hobbies |
| Savings / Debt | 20% | Emergency fund, retirement, extra payments |
Common Measurement Conversions for Everyday Use
| Quantity | US / Imperial | Metric Equivalent |
|---|---|---|
| 1 cup | 8 fl oz | 237 mL |
| 1 pint | 16 fl oz | 473 mL |
| 1 quart | 32 fl oz | 946 mL |
| 1 gallon | 128 fl oz | 3.785 L |
| 1 lb | 16 oz | 453.6 g |
| 1 ft | 12 in | 30.48 cm |